Filter assembly

ABSTRACT

The fuel filter assembly for filtering and removing water from a fuel under pressure includes an outerhousing, an inner sleeve member, an annular space between the outerhousing and the inner sleeve member, and filtering means for filtering the fuel. The filtering means is positioned within the sleeve member. The fuel inlet is at the upper end of the outer housing and provides fluid flow between the outer housing and the inner sleeve. The fuel inlet and annular space are positioned and dimensioned to provide a downward, non-circumferential, substantially laminar flow in the annular space. The inner sleeve member extends downwardly to a position below the bottom of the filtering means. The downwardly flowing fuel and contaminants must turn 180 degrees and flow upward through the filter media to the outlet. The slow moving denser components settle out in the accumulation chamber. The accumulation chamber is the region within the lower end of the outerhousing, below the filter media and the annular sleeve. The outlet valve provides a fluid drain for materials which accumulate in the accumulation chamber. The filtering means can be a hydrophobic filter media that prohibits the passage of water through the filter media.

This application is a divisional of Ser. No. 09/342,762 filed on Jun.29, 1999, now U.S. Pat. No. 6,203,698 which is a continuation of Ser.No. 08/942,997 filed on Oct. 2, 1997, now U.S. Pat. No. 5,916,442.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a fuel filter, and more particularly, to afilter for use with diesel fuel, and in particular, to a waterseparating fuel filter.

2. Brief Description of the Prior Art

In U.S. Pat. No. 4,986,907, it is stated that the design of the filteris such that the interior fuel flow conduit is an elongated pipe whoseperpendicular arrangement with respect to a longitudinal axis of theintake orifice allows a first impact of the fuel that enters theapparatus through the intake orifice. On flowing out from the interiorpipe 30, the fuel hits against metal plate 50 (sectioned vertically inFIG. 3), which runs diametrically and also substantially longitudinallyaround the interior of the cylinder. While the diesel filter of thepatent does a credible job of removing water, it is an expensivestructure and does not remove trace portions of water. It also fails tocompletely separate water if the water is accumulated as a large slug.Also, entrapped air interferes with the water separation process.

According to the patent the fuel that leaves pipe 30 and hits againstthe plate is projected centrifugally to create a turbulence thatinitially facilitates separation of its components such as water,sulfur, sulfuric acid, etc. which, due to their greater specific weightin relation to the (diesel) fuel tend to be precipitated toward thebottom surface of cylinder 10.

The concept of using centrifugal force to facilitate fuel/waterseparation, is also found in U.S. Pat. No. 4,780,203, in which fuelflows obliquely downward to generate a rotational flow promotingseparation of the denser water fraction from the fuel. An upturned lipis provided to collect water droplets that drift down the outer surfaceof the outlet conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the instant disclosure will become more apparent whenread with the specification and the drawings, wherein:

FIG. 1 is a cross-sectional view of a filter assembly in accordance withthe present invention.

FIG. 2 is a schematic illustration of a filter media.

FIG. 3 is a cross-sectional view of an alternate filter assembly.

SUMMARY OF THE INVENTION

It has now been found that a fuel filter can be produced at a very lowcost by scrupulously avoiding the turbulent flow found in prior artfilters, such as U.S. Pat. Nos. 4,986,907 and 4,780,203. Additionally,it has been found that the instant design can provide equivalentperformance or even superior performance with a smaller diameter unit.That is, the use of an equivalent diameter to that typically employedwith the '907 design provides superior performance. In the design of theinstant invention, water is completely removed regardless of the waterslug size, until the contaminant chamber is filled.

The fuel filter assembly for filtering and removing water from a fuelunder pressure includes an outerhousing, an inner sleeve member, anannular space between the outerhousing and the inner sleeve member, andfiltering means for filtering the fuel. The filtering means ispositioned within the sleeve member. The fuel inlet is at the upper endof the outer housing and provides fluid flow between the outer housingand the inner sleeve. The fuel inlet and annular space are positionedand dimensioned to provide a downward, non-circumferential,substantially laminar flow in the annular space. The inner sleeve memberextends downwardly to a position below the bottom of the filteringmeans. The downwardly flowing fuel and contaminants must turn 180degrees and flow upward through the filter media to the outlet. The slowmoving denser components settle out in the accumulation chamber. Theaccumulation chamber is the region within the lower end of theouterhousing, below the filter media and the annular sleeve. The outletvalve provides a fluid drain for materials which accumulate in theaccumulation chamber.

The filtering means can be a hydrophobic filter media that prohibits thepassage of water through the filter media.

DETAILED DESCRIPTION OF THE INVENTION

The construction and use of the filter medium is well known in the art,as seen for example in U.S. Pat. No. 5,507,942. According to the '942patent, in order to provide a constant level of least possible fuel flowrestriction through the fuel filter assembly over the life of the filtermedia while utilizing the least possible amount of filter media, thefilter media is housed vertically in the housing 12 so that the lowerportions of the filter media become obstructed first before the fuellevel rises and utilizes unobstructed upper portions of the filtermedia. A filter canister houses the filter media which is folded backand forth in a circular fashion so that a hollow cylinder is formed. Thefilter media, in the top view, the filter has a star, or sunburstappearance, resulting from the folding of the filter media. According tothe '942, the filter media can also be continually rolled or wound abouta vertical axis or reference cylinder to form a hollow cylinder havingsubstantially concentric layers of filter media layered adjacent to oneanother.

The filter media can be fabricated from a paper based material, but anyother suitable material, such as fiberglass, plastics, etc., may beutilized to provide the proper filtering characteristics while alsobeing combustible for efficient disposal. In another embodiment, thefilter media can be a hydrophobic filter media that prohibits thepassage of water through the filter media. This can further facilitateprecluding water from passing through the fuel filter assembly andeffecting the performance of the engine or damaging fuel injectionmechanisms of the engine. The fuel filter media disclosed in '942 andother patents, can readily be employed in the filter of the presentinvention.

The instant invention departs from the structure and functioning ofprior art filters in that it provides laminar flow of fuel downwardalong a cylindrical sleeve. By laminar flow it is meant that there is anonturbulent flow of a viscous fluid in layers near a boundary, as thatof lubricating oil in bearings. Turbulent flow causes dirt particles andwater to be entrained in the fuel stream and works against theseparation process, where the dirt and water must pass through aturbulent stream of fuel during the separation step. It is believed thatthe centrifugal forces found in the prior art structures will separatedense materials from light materials, but unless, the separated streamsare maintained as discreet streams, reentrainment occurs. In the presentstructure, the flow inlet at the top of the filter, does not produce acentrifugal action. Additionally, the annular space between thecylindrical sleeve and the inside wall of the housing, has across-sectional area which is sufficiently large to provide for laminarflow. Additionally, the speed of the fuel flow is dramatically reduced,thereby enhancing the separation process. The dense water and particularmatter is directed downwardly along the sleeve. The rapid flow directionchange results in the lighter materials, that is, the fuel, to be drawnupwardly more readily than the denser water. Reentrainment of theseparated materials is not observed, when the system is in use. The useof a clear housing enables a user to view the flow patterns in thefilter structure. It is observed that air bubbles do not adverselyaffect the separation process. Additionally, adding extremely largequantities of water to the fuel, for demonstration purposes, in therange between a half pint and a pint of water, for a one quart filter(12 inch circumference), did not adversely affect the operation of thesystem. The separation was immediate and complete. Whereas in a systemsuch as seen in the U.S. Pat. No. 4,986,907, patent, water can be seenpassing through the system, particularly when there is entrained air orvery large quantities of water, the present system appears to beunaffected by air bubbles or the presence of a full accumulationchamber, provided that the water level is not above the turn aroundpoint. It is estimated that a 12 inch diameter filter of the presentinvention would be at least equivalent to a 16 inch diameter filter ofthe '907 design.

In U.S. Pat. No. 4,780,203 it is recognized that smaller droplets aremore difficult to separate from the main stream, than large droplets. Itis believed that this problem is due to the presence of the fluids in aswirling path which reentrains the smaller droplets. No such problem wasencountered in the filter system of the instant invention. It alsoappears that with a laminar flow environment small droplets of water orair coalesce thus, facilitating the separation process.

The annular flow provides not only for a change in flow direction, butcritically, provides for a flow rate change which is sufficient to allowfuel contaminants e.g. water and particulate to separate or fall outfrom the diesel fuel. By way of contrast, in U.S. Pat. No. 4,986,907, acentrifugal flow is produced which produces turbulent flow. The annularflow of the instant invention is vertically downward around the filter,and then vertically upward and through the filter. Turbulent flowentrains the water/particulate in the fuel and works against theseparation. The annular flow is laminar flow. The cross-sectional areaof the annular region is substantially less than that of the flowinterior. The flow rate change in combination with the flow directionchange, achieves the water/particulate-fuel separation. The rate of flowchange is in the range from about 1/20 to about 1/50, and preferably isin the range from about 1/30 to about 1/40. The flow speed change isinversely proportional to the cross sectional area size. Flow rate,typically in gallons per minute, to remain constant will experiencespeed changes relative to the cross directional square area of the flowcavity size. When the cross-sectional area is cut in half, the flowspeed must double to maintain a constant flow rate. The flow ratedecrease from 1, the inlet flow, to 1/20, the downward annular flow, to1/50, the upward annular flow, requires a corresponding cross-sectionalarea increase for each speed reduction. After the fuel reverses itsdownward, annular flow to the upward flow, the flow speed decreases dueto the additional area increase. The flow speed in the verticaldirection does not have the same level of criticality because theseparation has already taken place.

The change in flow direction, by itself, can produce separation. Theflow rate change also produces water/contaminant-fuel separation. Thecombination, optimizes the degree of separation which is achieved. Inthe optimum system, the separation can be essentially 100%. Theforegoing system minimizes or eliminates turbulent flow. Turbulent flowcauses water and other separated particles to be physically entrained inthe fuel, thereby working against the separation.

The flow in the instant system is maintained parallel to the walls, soas to avoid turbulent flow. The centrifugal-turbulent flow of the U.S.Pat. No. 4,986,907, is avoided.

The flow is from about a half square inch feed pipe to a region between5 inch ID outer wall and 4.5 inch OD inner wall. The annular flow isthus from a 0.5 sq. inch pipe to a 15 square inch annular area. The flowat the contaminant storage region increases to a 65 square inch area.Gravitational forces are used to enhance the separation. The flow rateafter the turn upward, is determined by the annular space around thefilter, between the filter and the annular tube, (the inner annulus),and is not narrowly critical. The inner annulus cross-sectional areashould be at least equal to the cross sectional area of the inlet andoutlet pipes. The separation take place prior to and during the flowdirection change. Therefore, the flow characteristics of the secondannulus need only be at least equal to the flow rate in the remainder ofthe system. The cross sectional area of the inner annulus thus is atleast equal to the cross sectional area of the inlet and outlet pipes. Areduced cross-sectional area would produce an undesirable restriction inthe system.

It is noted that in the U.S. Pat. No. 4,986,907, the particles must passthrough centrifugal flowing turbulent fluid. By way of contrast, thedownward flow in the instant invention is laminar. Thus the particlesare going from a region of laminar, reduced flow speed, into acollection region, an area of further reduced speed. In U.S. Pat. No.4,986,907, the flow is into a turbulent region, to a collection area andthen upward.

The installation of the filter upside down would negate the operation ofthe filter, since the filter uses gravity to assist in the separation.In a reversed flow installation, the heavy particles, (water and dirt)would try to flow against the flow direction of the fuel and thus wouldtend to be reentrained. This would be comparable to the centrifugalturbulent flow in the '907 patent. Thus, the inlet at the top achieves adownward, gravity assisted flow and separation. The diesel fuel upwardflow, leaves the water/particulate in the contaminant storage region.The terms top and bottom, referring to the inlet at the top and the ballvalve drain at the bottom, are relative to the gravity flow. That is,gravity flow is from top to bottom.

The collected water and dirt or other solid particle contaminants can bedischarged through the ball valve drain G.

The filter is a common paper filter, currently in use with diesel fuelengines. The ball valve drain, is a commercially available device and isnot of a critical design.

In the '907, area entrainment interferes with the water-fuel separation.In the present device, the air is not a significant problem, due to theabsence of turbulent flow. Additionally, the instant design provides foraccumulated air to flow upward and outward. The mounting of the filterbelow the height of the gas tank, enables the accumulated air to vent tothe gas tank.

The embodiment of FIG. 3, illustrates a two part filter, indicatedgenerally as 300. The upper unit 302, is essentially identical to thecorresponding portions of the filter of FIG. 2.

The lower portion 304 of the filter 300, differs from the lower portionof the filter of FIG. 2, in that it contains a concave plate 312, whichcan be termed, a false bottom. Concave plate 312 serves as a separatorwall between separated water and the fuel flowing or stored in the upperportion 302, of the filter 300. During the separation process, thediesel fuel, which is lighter than water, flows up and out of thefilter, through the filter medium, 322. The water, which is lighter thanthe diesel oil, gravitates to the bottom of the filter, passes throughthe opening 314, in the concave plate 312, and is housed within thelower water storage region 322, is defined by the concave plate 312 andthe lower section 304 of the filter unit 300. The lower storage region322, is provided with one or more vents, which permit diesel fueltrapped in the water storage region 322, to vacate the storage regionand for water to flow into the storage region. The vent 316 works inmuch the same way air vents work in commonly employed liquid storagecontainers. During the start-up period, the entire filter is filled withdiesel fuel. When fuel flow starts, the water is separated from thefuel, migrates downwardly by gravity, as indicated by arrow 318, andenters the water storage region 322 through the opening 314. Diesel fuelin the water storage region 322, leaves the storage region by means ofthe vent 320, as indicated by arrow 320.

A primary benefit derived from separating the diesel fuel and theseparated and stored water 320, is the prevention of reentrainment ofthe stored water 320.

The concave shape of the separator wall 312, is beneficial because theflow of water is directed, or naturally flows toward the opening in theconcave wall 312.

The water storage region 322 can be provided with one or more watersensors 308 and 310. When the water level reaches the sensor, a signalis provided to indicate that water drainage is required obviously, thedrainage can be automatic, and the water drainage valve 340, can be anelectrically operated valve. The automatic opening of the drainage valve340 causes the stored water to leave the filter 300. The dischargedwater can be stored in a separator water container, not shown. Theelectrically operate valve 340 can be time to remain open for a timeperiod sufficient to drain water from the water storage region.Preferably, the timer is set to close the valve prior to the completedrainage of water, so that fuel is not drained from the system.

The water storage region is seen to operate when the filter is in avertical position. However, if the filter is used in a vehicle whichwill be subjected to off-road use, the filter must be capable ofoperating at some offset angle. This condition can be encountered, evenmore readily, when the filter is used in boats.

In trucks, or other road operated vehicles, it would be unusual tosubject the vehicle to a substantial side to side pitch. The vehiclecould be required to climb or descend at a steep angle, however. In thisinstance, the use of a fore and aft water sensor would suffice. In aboat, side to side pitching can be expected and the sensors arepreferably a pair of sensors positioned side to side, relative to theboat. In speed boats, it can be desirable to use four sensors, toaccommodate the steep pitch of the boat during acceleration.

Since other modifications and changes varied to fit particular operatingrequirements and environments will be apparent to those skilled in theart, the invention is not considered limited to the example chosen forthe purposes of disclosure, and covers all changes and modificationswhich do not constitute departures from the true spirit and scope ofthis invention.

What is claimed:
 1. The method of separating a first liquid from asecond liquid under pressure comprising the steps of: passing a firstliquid and a second liquid through a liquid inlet to a first downwardflow region, said second liquid being lighter than said first liquid,subjecting said first liquid and said second liquid to a downward,non-circumferential, substantially laminar flow in a said first downwardflow region, diverting said laminar fluid flow of said second fluidupwardly to a first upward flow region, said first upward flow regionsbeing concentric with said first downward flow region, and divertingsaid laminar flow of said first fluid downward to a first fluidaccumulation region, thereby separating said first liquid from saidsecond liquid in the laminar flow region of the end of said firstdownward flow region, removing said first liquid from said first fluidaccumulation region through a first liquid outlet, and flowing saidsecond said second liquid though said first upward flow region andthrough a filter medium, said filter medium being coaxial andsubstantially coextensive with said first downward flow region and outof said first upward flow region through a second liquid outlet.
 2. Themethod of claim 1, wherein said first liquid is water, and said liquidis a liquid fuel.
 3. The method of claim 2, wherein said first liquidfuel is diesel fuel.